Polyester resin composition and light-reflecting molded article thereof

ABSTRACT

A light-reflecting molded article is constituted of a molded article made from a polyester resin composition and a light-reflecting metal layer formed on the molded article. The light-reflecting molded article has an average surface roughness of at most 0.3 μm and a deflection temperature under load of at least 160° C. The polyester resin composition includes 100 parts by weight of polybutylene terephthalate resin and 1 to 100 parts by weight of polyalkylene naphthalate resin.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to polyester resin compositionsused for light-reflecting molded articles. More specifically, theinvention relates to a polyester resin composition from which a moldedarticle having a highly glossy surface is produced with a relativelysmall amount of gas generated in the molding process. The small amountof generated gas allows a light-reflecting metal layer to be formeddirectly on the molded article without undercoating therebetween. Theresultant molded article is excellent in specular reflection propertiesand luminous brightness and further excellent in maintenance of itssurface appearance when used under high temperatures (i.e. thermalresistance) as well as adhesiveness to the metal layer. Thelight-reflecting metal layer is formed on the molded article by coatingand/or vapor deposition.

[0003] The polyester resin composition according to the presentinvention is suitably used for lamp-related parts in the fields ofautomobile, building equipment and various industries. In particular,this polyester resin composition is suitably used for lamp reflectors,extensions and the like which are lamp-related parts of automobilesrequired to have high surface luminous brightness, smoothness and lightreflectance.

[0004] 2. Description of the Background Art

[0005] A light reflector, particularly for an extension, for example,which is one of lamp-related parts of an automobile is usually requiredto have high luminous brightness and smoothness, uniform lightreflectance, high thermal resistance and the like for the directionaland reflective properties of a lamp source. Accordingly, a crystallinethermoplastic polyester resin which is superior in mechanical andelectrical properties as well as physical and chemical properties andfurther excellent in processability has been used as a material fromwhich such a reflector is produced. In particular, a polybutyleneterephthalate resin is used solely or used as a mixture thereof with apolyethylene terephthalate resin to which various reinforcing agents areadded and blended therewith. A pretreatment such as undercoating isapplied to a resultant molded article and thereafter a light-reflectingmetal layer is formed thereon by means of vacuum deposition for exampleand thus a desired light reflector is produced.

[0006] The undercoating, however, leads to a considerable increase incost, and thus a light reflector without undercoating that stillexhibits a high luminous brightness and has a highly dense depositedlayer is desired. In order for a reflector, which is formed of a moldedarticle having at least one surface provided with a light-reflectinglayer without undercoating therebetween, to have a high luminousbrightness and a uniform reflectance, it is necessary that the resinmolded article itself exhibits a superior surface smoothness as well ashigh gloss and luminous brightness.

[0007] Moreover, in terms of applications of the reflector, the thermalresistance of resin is an important issue. In general, the polybutyleneterephthalate resin has a high crystallization speed and thus issolidified relatively quickly in a mold. Therefore, it is difficult toachieve a satisfactory specular transcription. In addition, wheninorganic fillers such as talc and mica are added to the resin forproviding a thermal resistance thereto, such fillers could be isolatedand become visible (appearance on the surface). Then, according to amethod employed for producing a molded article excellent in gloss andsurface properties, the method being devised in consideration ofmaterials for the molded article, an amorphous polymer is added to thepolybutylene terephthalate resin in order to lower the crystallizationspeed thereof and thus improve the mold transcription and furtherprevent the filler from being isolated and becoming visible (appearanceon the surface).

[0008] There are also methods devised in consideration of the moldingprocess. For example, according to one of such methods generallyemployed, the resin temperature is increased to enhance the flowability.According to another method, the mold temperature is increased to lowerthe crystallization speed and thus improve the mold transcription.Although those methods improve the appearance of the molded article tosome degree, the increased resin temperature and the increased moldtemperature result in a noticeable generation of gas in the moldingprocess and accordingly cause any defect in the appearance such astarnishing (haze) on the surface of the molded article. Therefore, thesemethods cannot successively produce satisfactory molded articles andrequire additional polishing, wiping and the like of the mold. Further,the addition of the amorphous polymer deteriorates, if the amorphouspolymer itself has a low thermal resistance, the surface and luminousbrightness properties of the molded article when used under hightemperatures, so that the molded article employed as a light reflectorhas a deteriorated thermal resistance level. Moreover, an amorphouspolymer with a high glass transition temperature generally has a lowsolublity with respect to the polybutylene terephthalate resin so thatsuperior surface properties are impossible to achieve.

SUMMARY OF THE INVENTION

[0009] One object of the present invention is to produce a polyesterresin composition used for a light-reflecting molded article having anexcellent luminous brightness and a high reflectance as well as asatisfactory adhesiveness to metal even if a light-reflecting metallayer is directly vapor-deposited on a resin molded article withoutundercoating, and further having a thermal resistance which allows suchproperties to be maintained when the molded article is used under hightemperatures. In order to accomplish this object, the inventors of thepresent invention have conducted dedicated studies to achieve thepresent invention.

[0010] The present invention is a light-reflecting molded articleconstituted of a molded article made from a polyester resin compositionand a light-reflecting metal layer formed on the molded article. Thelight-reflecting molded article has an average surface roughness of atmost 0.3 μm and a deflection temperature under load of at least 160° C.

[0011] The present invention is a polyester resin composition from whicha molded article is made, a light-reflecting metal layer being formed onthe molded article to produce a light-reflecting molded article. Thepolyester resin composition includes 100 parts by weight of polybutyleneterephthalate resin (component A) and 1 to 100 parts by weight ofpolyalkylene naphthalate resin (component B).

[0012] According to the present invention, the polybutyleneterephthalate resin (component A) has a content of carboxyl group at theend of polymer chain that is at most 70 meq/kg.

[0013] Preferably, at least 75% by molar fraction of a 1,4-butanediolunit is contained in the total diol component of the polyalkylenenaphthalate resin (component B).

[0014] According to the invention, the polyester resin compositionincludes 100 parts by weight of polybutylene terephthalate resin(component A) and 1 to 50 parts by weight of polyalkylene naphthalateresin (component B).

[0015] Preferably, the light-reflecting metal layer is formed by vapordeposition to exhibit specular gloss. Still preferably, metal in thelight-reflecting metal layer is aluminum.

[0016] Moreover, according to the present invention, the molded articlehas at least a part thereof on which the light-reflecting metal layer isdirectly formed.

[0017] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A polyester resin composition according to the present inventionhas a structure described in detail below.

[0019] The present invention is a light-reflecting molded articleconstituted of a molded article made from a polyester resin compositionand a light-reflecting metal layer formed on the molded article. Thelight-reflecting molded article has an average surface roughness of atmost 0.3 μm and a deflection temperature under load of at least 160° C.

[0020] The average surface roughness of the molded article relates todiffuse reflection of light and affects the luminous brightness of themolded article. It is thus required that the average surface roughnessis at most 0.3 μm, preferably at most 0.28 μm. Further, the deflectiontemperature under load relates to deterioration, due to deformation ordeflection, of light orientation and adhesiveness to metal. Around alamp, the temperature is at least 160° C. and preferably at least 170°C.

[0021] The molded article of the present invention as described above issuitably produced by using a polyester resin composition including 100parts by weight of polybutylene terephthalate resin (component A) and 1to 100 parts by weight of polyalkylene naphthalate resin (component B).

[0022] <Polybutylene Terephthalate Resin>

[0023] According to the present invention, polybutylene terephthalateresin refers to a polybutylene terephthalate produced throughpolycondensation of terephthalic acid or its ester-formable derivativeand alkylene glycol of carbon number 4 or its ester-formable derivative.Preferably, the polybutylene terephthalate may be a copolymer containingat least 70% by weight of a butylene terephthalate unit in its molecularchain.

[0024] In the copolymer, a monomer is included as a dibasic acidcomponent other than the terephthalic acid and its lower alcohol ester,and the monomer used here is aliphatic acid or aromatic polybasic acidsuch as isophthalic acid, naphthalene dicarboxylic acid, adipic acid,sebacic acid, trimellitic acid and succinic acid, and theirester-formable derivatives, for example.

[0025] In the copolymer, a glycol component other than 1,4-butanediol isincluded, and the glycol component used here is general alkylene glycolsuch as ethylene glycol, diethylene glycol, propylene glycol,trimethylene glycol, hexamethylene glycol, neopentyl glycol andcyclohexane dimethanol, lower alkylene glycol such as 1,3-octanediol,aromatic alcohol such as bisphenol A and 4,4′-dihydroxy biphenyl,alkylene oxide adduct alcohol such as ethylene oxide 2-mol adduct ofbisphenol A and propylene oxide 3-mol adduct of bisphenol A, polyhydroxycompound such as glycerin and pentaerythritol, or its ester-formablederivative, for example.

[0026] According to the present invention, component A can be thepolybutylene terephthalate produced by polycondensation of the compoundsas described above as monomer components, or the copolymer containingpolybutylene terephthalate and other bonding units of monomers.Component A contains polybutylene terephthalate solely or at least twotypes thereof which are mixed. Preferably, a polybutylene terephthalatehomopolymer is used.

[0027] Further, according to the present invention, a branching polymerwhich is one of the copolymers may be used. For example, a polyestersuch as polybutylene terephthalate branching polymer may be used whichmainly contains polybutylene terephthalate or butylene terephthalatemonomer to which a multifunctional compound is added for branching.Examples of the multifunctional compound are trimesic acid, trimelliticacid, pyromellitic acid and alcohol ester thereof, glycerin,trimethylolethane, trimethylolpropane and pentaerythritol.

[0028] Preferably, the content of carboxyl group at the end of polymerchain in the polybutylene terephthalate resin of the present inventionis preferably 70 meq/kg or less. More preferably, the content is 40meq/kg or less, and still more preferably 30 meq/kg or less. The contentof carboxyl end group that is 70 meq/kg or less provides a remarkablereduction of haze on a resultant molded article, and thus such a contentis particularly preferable for application to light-reflecting moldedarticles.

[0029] The carboxyl group content is measured by using a sample obtainedby crushing polybutylene terephthalate resultant from polycondensationof monomers as described above, dissolving the sample in benzyl alcoholat 215° C. for 10 minutes, and thereafter determining the content bytitration using a 0.0 1N aqueous solution of sodium hydroxide.

[0030] The polybutylene terephthalate resin according to the presentinvention has a weight-average molecular weight (Mw) ranging from 10,000to 50,000 and a specific reduced viscosity ranging from 0.5 to 2.0 dl/g.

[0031] Here, the specific reduced viscosity is measured by the followingmethod. A solvent mixture of phenol and tetrachloroethane with theweight ratio of 6:4 is used, and, under conditions of a temperature of30° C. and a concentration of 0.4 g/dl and by means of an Ostwaldviscometer, the falling time is measured through comparison with thesolvent.

[0032] <Polyalkylene Naphthalate Resin>

[0033] The polyester resin composition according to the presentinvention contains component A as detailed above with which polyalkylenenaphthalate resin (component B) is blended. The polyalkylene naphthalateresin (component B) blended with the polybutylene terephthalate resin(component A) is a requisite component for improvement of suchproperties as surface smoothness and luminous brightness of resultantmolded article and light-reflecting metal layer. Polyalkylenenaphthalate has a lower crystallization speed and a smaller coefficientof linear expansion than those of polybutylene terephthalate and isaccordingly effective because it improves the mold transcription of theresin composition when blended therein. Moreover, polyalkylenenaphthalate has a higher deflection temperature under load than that ofpolybutylene terephthalate and is thus effective because it preventsdeterioration of the surface smoothness and luminous brightness as wellas deformation, for example, when the molded article having thelight-reflecting layer is exposed to high temperature like light andheat. In view of these two effects described above, the polyalkylenenaphthalate resin is a requisite component for the present invention forachieving a light-reflecting article of superior appearance.

[0034] The polyalkylene naphthalate resin (component B) according to thepresent invention is a polymer produced by polycondensation ofnaphthalic acid or its ester-formable derivative and alkylene glycol ofcarbon number 2 to 8 or its ester-formable derivative. Preferably, thepolyalkylene naphthalate resin may be a copolymer containing at least 70mol % of an alkylene naphthalate unit in its molecular chain.

[0035] The copolymer of polyalkylene naphthalate resin according to thepresent invention contains a monomer as an acid component other thannaphthalenedicarboxylic acid that is specifically aliphatic acid oraromatic polybasic acid such as terephthalic acid, isophthalic acid,adipic acid, sebacic acid, trimellitic acid and succinic acid and theirester-formable derivatives, for example. Preferred acid components arenaphthalenedicarboxylic acid, terephthalic acid and isophthalic acid. Inparticular, only the naphthalene dicarboxylic acid is used.

[0036] The polyalkylene naphthalate resin according to the presentinvention contains, as a diol component, general alkylene glycol such asdiethylene glycol, propylene glycol, 1,4-butanediol, hexamethyleneglycol, neopentyl glycol and cyclohexane dimethanol, lower alkyleneglycol such as 1,3-octanediol, alkylene oxide adduct alcohol such asethylene oxide 2-mol adduct of bisphenol A and propylene oxide 3-moladduct of bisphenol A, polyhydroxy compound such as glycerin andpentaerythritol, or its ester-formable derivative, for example.Preferred diol components are ethylene glycol, propylene glycol and1,4-butanediol. In particular, only the 1,4-butanediol is used.

[0037] The polyalkylene naphthalate resin described above has aweight-average molecular weight (Mw) ranging from 5,000 to 50,000 and aspecific reduced viscosity ranging from 0.5 to 2.0 dl/g.

[0038] According to the present invention, with 100 parts by weight ofthe polybutylene terephthalate resin (component A), 1 to 100 parts,preferably 1 to 50 parts, and more preferably 15 to 40 parts by weightof the polyalkylene naphthalate resin is blended.

[0039] Less than 1 parts by weight of component B is not preferablesince it results in a smaller effect of reducing the coefficient oflinear expansion, and a required luminous brightness is not attained.More than 100 parts by weight of component B causes the resin to beadhered closely to the mold and thus leads to failure in molding, orconsiderably extends the cooling time, so that the moldabilitydeteriorates to a great degree, and accordingly is not preferable. Inaddition, this is inappropriate for practical use because of a lowercost efficiency.

[0040] <Additives>

[0041] Moreover, according to the present invention, an antioxidant maybe added for enhancing the thermal stability of the resin compositionconstituting the light reflector when the resin composition is beingmolded and for preventing the appearance and luminous brightness fromdeteriorating due to gas generated from the resin compositionparticularly when compositions are successively molded, low molecularweight component and any component appearing on the surface, forexample.

[0042] Preferably, the antioxidant employable according to the inventionis one or a combination of at least two selected from hindered phenols,thioethers and organic phosphates. Addition of such an antioxidant iseffective for improvement of the melt thermal stability in an extrudingprocess or in a molding machine and advantageous in that molded articleswith less surface haze and excellent appearance and surface propertiesare successively produced. Further, addition of the antioxidant isparticularly advantageous, when the light reflector is under hightemperature conditions, in that gas is prevented from being generatedfrom the resin and generation of any decomposed material is avoided, andthus satisfactory appearance and surface properties are maintained.

[0043] Specific examples of the employed antioxidant are as follows.Examples of hindered phenol aretetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane,triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionateand 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],for example. Examples of thioether aretetrakis[methylene-3-(dodecylthio)propionate]methane,dimyristylthiodipropionate and didodecylthiodipropionate, for example.Examples of organic phosphate are bis(2,6-di-t-4-methylphenyl)pentaerythritol diphosphate, bis(2,4-di-t-butylphenyl)pentaerythritoldiphosphate, tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene phosphate,and tris(2,4-di-t-butylphenyl)phosphate, for example. Particularlyeffective combinations are a combination of hindered phenol andthioether, a combination of hindered phenol and organic phosphate and acombination of the three types of antioxidants.

[0044] Instead of the antioxidant of organic phosphate, metal phosphateis preferably employed such as monohydrates of calcium primary phosphateand sodium primary phosphate.

[0045] Further, according to the present invention, one or at least twocompounds may be added for improving the mold releasability of a productin a molding process and enhancing the appearance of the molded product.Specifically, the compound(s) is (are) selected from fatty acid esters,typical examples thereof being glycerin fatty acid esters, sorbitanfatty acid esters, stearates and montanoic acid esters, and partiallysaponified compounds thereof, polyether-based compounds, higher fattyacid metal salts, trimellitic acid esters, and pyromellitic acid esters.

[0046] To 100 parts by weight of the polybutylene terephthalate(component A), 0 to 2.0 parts by weight of the compound(s) as describedabove are added. A greater amount of such compounds added to component Acould result in noticeable haze and any material appearing on thesurface depending on the temperature in use and thus is not preferable.

[0047] According to the present invention, an inorganic reinforcingagent may be added for improving the thermal resistance for example. To100 parts by weight of the polyester resin composition, less than 10parts by weight of the inorganic reinforcing agent may be added.Specific examples of the reinforcing agent are fibrous reinforcingagents such as glass fiber and carbon fiber, potassium titanate, andinorganic fillers such as talc, warastnite, silica, clay, calciumcarbonate and glass beads. At least one of those reinforcing agents maybe added to the resin composition of the present invention.

[0048] In addition, the composition of the present invention may containwell-known additives which are generally added to a thermoplastic resinfor example in order to add desired characteristics to the resindepending on applications thereof. For example, antistatic agent,mold-releasing agent and coloring agents like dye and pigment, forexample, may be added to and blended with the resin composition.

[0049] <Preparation of Composition>

[0050] The composition of the present invention is readily prepared bymeans of facilities and method that have commonly been employed forpreparing a resin composition. Various methods are available, forexample, (1) components of predetermined amounts respectively thatconstitute the composition of the present invention are mixed alltogether, melted and kneaded by a monoaxial or biaxial extruder toproduce a pellet having an intended composition, (2) by means of amonoaxial or biaxial extruder having at least two openings through whichmaterials are supplied, resin, stabilizer, pigment components forexample are provided from the first opening and they are melted andkneaded, an inorganic filler is thereafter provided from the secondopening, melted and kneaded, and thus a pellet with an intendedcomposition is produced, or by any of other applicable methods.

[0051] The composition of the present invention can be molded into amolded article by such methods as injection molding and injectioncompression molding. The injection molding method is generally employed.

[0052] A light-reflecting metal layer can be formed on the moldedarticle for example by sputtering, or vacuum deposition. Here, the layerdeposited thereon has a thickness of at most 0.1 μm.

[0053] According to the present invention, examples of the metalconstituting the light-reflecting metal layer are gold, silver, copper,aluminum, tin, lead, zinc, platinum, titanium, manganese, chromium,iron, nickel, cobalt, silicon, germanium, gallium, molybdenum, and alloycontaining such metals by at least 50%. In particular, aluminum andaluminum alloy are preferred according to the invention.

EXAMPLES

[0054] The present invention is now described specifically by means ofexamples. However, the invention is not limited to such examples. Itemsused for making evaluations were determined by the methods as detailedlater below. Here, “parts” and “percent (%)” employed for representingthe amounts of components refer to “parts by weight” and “percent byweight” respectively.

[0055] Components blended for producing the composition were as follows.

[0056] Thermoplastic polyester resin:

[0057] <Polybutylene Terephthalate Resin>

[0058] PBT-1: polybutylene terephthalate resin manufactured by TorayIndustries, Inc. under the name of Toraycom, with η_(sp)/c of 1.23 andthe content of carboxyl group at the end of polymer chain (CEG content)of 30 meq/kg

[0059] <Polybutylene Terephthalate Resin>

[0060] PBT-2: polybutylene terephthalate resin manufactured by TorayIndustries, Inc. under the name of Traycom with η_(p/)c of 0.85 and theCEG content of 80 meq/kg

[0061] <Polybutylene Naphthalate Resin>

[0062] PBN: polybutylene naphthalate resin manufactured by Toyobo. Co.,Ltd. with η_(sp)/c of 0.88

[0063] <Polyethylene Naphthalate Resin>

[0064] PEN: polyethylene naphthalate resin manufactured by Toyobo. Co.,Ltd. with η_(sp)/c of 0.75

[0065] <Polycarbonate Resin>

[0066] PC: polycarbonate manufactured by Sumitomo Dow Limited under thename of Calibre 301, with a melt flow rate (300° C., 1.18N) of 6 g/min

[0067] Inorganic reinforcing agent:

[0068] talc (grain size: 3.8 μm)

[0069] Fatty acid salt and/or fatty acid ester compound (referred to asWax):

[0070] Wax-1: manufactured by Clariant (Japan) KK under the name ofHostamont CaV 102

[0071] Wax-2: manufactured by Clariant (Japan) KK under the name ofHostalub WE 40

[0072] (1) Appearance Evaluation

[0073] A molding process was performed under the following moldingconditions, and a flat molded article of 100 mm×100 mm having athickness of 2 mm and a molded article of 125 mm×125 mm with a thicknessof 6.4 mm according to ASTM D648 were used.

[0074] Molding conditions:

[0075] Molding machine: Toshiba IS-80

[0076] Cylinder temperature (° C.) : 265-265-260-250

[0077] Injection speed: 2.0 m/min

[0078] Injection pressure: 400 kg/cm²

[0079] Mold temperature: 80° C.

[0080] (2) Vapor Deposition

[0081] A vapor deposition apparatus was used for vapor deposition of theflat molded article. The pressure within the deposition apparatus waslowered to 1.0×10⁻² Pa and aluminum was vapor-deposited at a speed of1.0 nm/sec to the thickness of 100 nm. The appearance of alight-reflecting surface of a light reflector thus produced was visuallyobserved and scores used for evaluation here were as follows.

[0082] Score 1: high luminous brightness, a fluorescent lamp clearlyseen in the surface without distortion

[0083] Score 2: high luminous brightness, a fluorescent lamp seen in thesurface without distortion, haze appearing slightly due to gas

[0084] Score 3: haze appearing to some degree due to gas, a fluorescentlamp seen in the surface without distortion, the lamp being somewhatblurred

[0085] Score 4: uneven surface causing a fluorescent lamp seen thereinto be distorted to some degree, haze appearing due to gas

[0086] Score 5: rough surface causing a fluorescent lamp seen therein toappear wavy, white haze appearing due to gas

[0087] In addition, the light reflector was left at 160° C. for 24 hoursand thereafter the appearance of the light-reflecting surface wasvisually observed and any score was given as described above.

[0088] (3) Surface Roughness

[0089] The flat molded plate (100 mm×100 mm×2 mm) used for theabove-described appearance evaluation was employed for determining theaverage roughness (μm) of ten points thereof and measuring the maximumheight (μm) by using a surface roughness measuring device (SURFCOM 554Amanufactured by Tokyo Seimitsu Co., Ltd.).

[0090] (4) Deflection Temperature under Load (heat distortiontemperature: HDT)

[0091] The temperature was measured according to ASTM D-648 (by using ameasurement weight for providing a fiber stress of 0.46 MPa).

[0092] (5) Cross-Cut Adhesion Test

[0093] The adhesiveness of the aluminum film, which was formed on theflat molded article through vapor deposition, to the flat molded articlewas evaluated as follows. The flat molded plate (100 mm×100 mm×2 mm) atroom temperature that was produced under the molding conditionsdescribed above and subjected to the vapor deposition by theabove-described method was left for 24 to 48 hours in a chamber with aconstant temperature of 23° C. and a constant humidity of 50%. For thecross-cut adhesion test, the film was cross-cut into a grid of 100sections at 1 mm intervals and an adhesive cellophane tape manufacturedby Nichiban Co., Ltd. was used. The cross-cut adhesion test wasconducted five times for one example or comparative example. The numberof remaining sections on the test plate surface was represented bypercentage to make an evaluation.

Examples 1 and 3-6, Comparative Examples 1-3

[0094] PBT-1 and PBN were used and respective contents of the inorganicreinforcing agent and mold-releasing agent for example were varied asshown in Table 1. A biaxial extruder having a cylinder with itstemperature set at 245-250-250-245° C., the first temperature being ofthe part closest to a nozzle, was used for melting and kneading thematerials into a pellet. The resultant pellet was dried at 135° C. for 4hours. After this, a molding machine with a cylinder temperature of 240to 260° C. was used for injection molding by means of a chromium-platedmold with a surface temperature of 90° C. Thus, a test plate forevaluation was produced. Table 1 and Table 2 show results ofevaluations.

Example 2

[0095] PEN was used instead of PBN of example 1. All of other conditionswere the same as those of example 1 to produce a test plate forevaluation through melting, kneading and injection molding. Results ofevaluations are shown in Table 1.

Example 7

[0096] PBT-2 was used instead of PBT- 1 of example 1. All of otherconditions were the same as those of example 1 to produce a test platefor evaluation through melting, kneading and injection molding. Resultsof evaluations are shown in Table 1.

Comparative Examples 4-7

[0097] Sheets to be evaluated were produced respectively throughmelting, kneading and injection molding as done for example 1, with thecontents of PBT-1 and PBT-2 changed. Results of evaluations are shown inTable 2.

Example 8

[0098] The resin composition prepared in example 1 was used. The resintemperature and the mold temperature were set respectively at 265° C.and 60° C., and a reflector and an extension for a car headlamp (asshown in FIG. 1 of Japanese Patent Laying-Open No. 8-208959) was formedby injection molding. Under a vacuum of 1×10⁻² Pa, aluminum was heatedto 1450° C. to be vapor-deposited on the entire surface. The resultantmolded article without primer exhibits a high luminous brightness.Further, a cross-cut adhesion test was conducted for determining theadhesiveness of the deposited layer, and no peeling was observed.

[0099] Moreover, the extension with a metal layer deposited thereon wasused for fabricating a lamp unit and a 168-hour continuous lighting testwas conducted. As a result, no deformation and no swelling of thedeposited layer were observed, which means a satisfactory thermalresistance was attained. TABLE 1 Example (E) E1 E2 E3 E4 E5 E6 E7 PBT-1parts 90 90 90 89.5 89.5 70 PBT-2 parts 90 PBN parts 10 10 10 10 25 10PEN parts 10 talc parts 5 5 Wax-1 parts 0.5 Wax-2 parts 0.5 0.5appearance of immediately after 1 1 1 1 1 1 2 light- vapor depositionreflecting 160° C./after 24hrs 1 1 2 2 1 2 2 surface surface 10-point av[μm] 0.15 0.18 0.27 0.22 0.14 0.24 0.29 smoothness roughness(immediately after vapor max height [μm] 0.27 0.29 0.37 0.35 0.24 0.360.37 deposition cross-cut immediately after 100 100 100 100 100 100 100adhesion test vapor deposition 160° C./after 24hrs 100 100 98 95 100 99100 deflection temperature [° C.] 173 176 187 170 174 176 152 under load(0.46 MPa)

[0100] TABLE 2 Comparative Example (CE) CE1 CE2 CE3 CE4 CE5 CE6 CE7PBT-1 parts 100 10 10 90 80 70 90 PBT-2 parts PBN parts 80 85 PC parts10 20 30 10 talc parts 10 Wax-1 parts 0.5 0.5 0.5 0.5 Wax-2 parts 5appearance of immediately after 1 3 2 1 1 1 1 light- vapor depositionreflecting 160° C./after 24hrs 4 5 5 4 4 5 4 surface surface 10-point av[μm] 0.36 1.31 0.28 0.31 0.26 0.25 0.22 smoothness roughness(immediately after vapor max height [μm] 0.4 1.46 0.42 0.38 0.30 0.300.28 deposition cross-cut Immediately after 100 100 80 100 100 98 100adhesion test vapor deposition 160° C./after 24hrs 100 95 25 100 100 92100 deflection temperature [° C.] 158 205 209 147 141 132 129 under load(0.46 MPa)

[0101] As heretofore discussed, the light-reflecting molded articleproduced from the polyester resin composition of the present inventionexhibits a remarkably high luminous brightness, less deterioration, dueto haze, of the luminous brightness under successive molding processesand high temperatures, and is excellent in adhesiveness to metal andthermal resistance. Such a light reflector is preferably applied toreflectors, extensions and the like of automobile lamps requiring a highreflectivity, and thus the reflector makes a great contribution to theindustry.

[0102] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

What is claimed is:
 1. A light-reflecting molded article constituted ofa molded article made from a polyester resin composition and alight-reflecting metal layer formed on said molded article, saidlight-reflecting molded article having, after being molded, an averagesurface roughness of at most 0.3 μm and a deflection temperature underload of at least 160° C.
 2. A polyester resin composition from which amolded article is made, a light-reflecting metal layer being formed onsaid molded article to produce a light-reflecting molded article, andsaid polyester resin composition including 100 parts by weight ofpolybutylene terephthalate resin and 1 to 100 parts by weight ofpolyalkylene naphthalate resin.
 3. The polyester resin compositionaccording to claim 2, wherein said polybutylene terephthalate resin hasa content of carboxyl group at the end of polymer chain that is at most70 meq/kg.
 4. The polyester resin composition according to claim 2,wherein at least 75% by molar fraction of a 1,4-butanediol unit iscontained in the total diol component of said polyalkylene naphthalateresin.
 5. The polyester resin composition according to claim 2, whereinsaid polyester resin composition includes 100 parts by weight ofpolybutylene terephthalate resin and 1 to 50 parts by weight ofpolyalkylene naphthalate resin.
 6. The polyester resin compositionaccording to claim 2, wherein said light-reflecting metal layer isformed by vapor deposition to exhibit specular gloss.
 7. The polyesterresin composition according to claim 2, wherein metal in saidlight-reflecting metal layer is aluminum.
 8. The polyester resincomposition according to claim 2, wherein said molded article has atleast a part thereof on which said light-reflecting metal layer isdirectly formed.